Duplications of large segments of noncoding [junk] DNA in the human genome may have contributed to the emergence of differences between humans and nonhuman primates, according to results presented at the American Society of Human Genetics (ASHG) 2017 Annual Meeting in Orlando, Fla. Identifying these duplications, which include regulatory sequences, and their effect on traits and behavior may help scientists explain genetic contributions to human disease.
Paulina Carmona-Mora, PhD, who presented the work; Megan Dennis, PhD; and their colleagues at the University of California, Davis, study the history of human-specific duplications (HSDs), segments of DNA longer than 1,000 base pairs that are repeated in humans but not in primates or other animals. In this study, they focused on HSD regions that do not code for genes, but instead regulate the expression of other genes.
“What’s special about these regulatory elements is that they have the propensity to impact the expression of genes nearby on the same chromosome, as well as elsewhere in the genome,” said Dr. Dennis. “This means that one duplication could affect many genes, amplifying its impact.”
Since duplicated segments are more than 98% identical, it is difficult to distinguish between them, Dr. Dennis explained. As a result, they were discarded in many past genomic analyses. For this reason, the researchers began by creating a new human reference genome that included the duplicated segments. This allowed them to identify areas likely to contain enhancers, which are regulatory elements that increase expression of other genes, and assess their effect on gene expression across organs and tissue types.
“Our results point to differences between humans and primates, and hint at what makes us unique as humans,” said Dr. Dennis. More.
So large elements of human non-coding DNA [junk, according to Darwinian experts of recent vintage] help distinguish humans from gorillas?
Some of us suspect that there is more to it than that. Transplanting these segments into the gorilla would not cause him to sit up and ask, “Why did I spend my life eating 50 tonnes of vegetation to date? Am I just a 400-lb vegetation conversion mechanism? Or is something else going on?” Press on.
See also: Researchers: “Junk DNA” lowers risk of heart disease
The “deteriorating” Y chromosome features new genes
Life continues to ignore what evolution experts say: “— Genome doubling. Some plants can duplicate their chromosomes (polyploidy) to foster explosive growth without undergoing cell division. Thus, they can recover quickly from damage, such as being half eaten by grazing animals. The process, long considered a major force in plant evolution, immediately gives the cells much more DNA to work with, favoring adaptation to challenging new circumstances.”